reciprocal bearing

reciprocal bearing

[ri′sip·rə·kəl ′ber·iŋ]
(navigation)

back beam

back beamclick for a larger image
A localizer with both front beam and back beam.
back beam
back beam
back beam
back beam
No change in back bearing in this case as the aircraft is flying directly south.
A reciprocal beam on the other side of a transmitter and on a reciprocal heading, as in an ILS (instrument landing system) localizer. Aircraft on a back beam may not have glide-path information.
back bearing
i. The horizontal angle, measured clock-wise from a datum, and observed from an aircraft for a point over which it has passed without an intervening alteration of a heading. It is the reciprocal of track.
ii. A bearing differing by 180°, or measured in the opposite direction from a given bearing. Also called a reciprocal bearing.
iii. The bearing at the opposite end of a line from the observer as measured from the true meridian at the opposite end of the line. The back bearing on all lines (other than north-south lines) differs from the bearing at the observer's station by the amount of convergency of the meridians between the two points.